Method and apparatus for reducing power required by moving suction box cover



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Aprll 25, 1961 E. J. JUSTUS 2,981,328

METHOD AND APPARATUS FOR REDUCING POWER REQUIRED BY MOVING SUCTION BOXCOVER Filed Jan. 14, 1958 2 Sheets-Sheet l 7 O A H be EZUT Edgar (jc/wizzs b H/AZZ/M/MMVW flrr s- April 25, 1961 E. J. JUS 8 2,981,328

METHOD AND APPARATUS F REDUCING POWER REQUIRED BY MOVING SUCTION BOXCOVER Filed Jan. 14, 1958 2 Sheets-Sheet 2 Zia 22.1fm?

' Edgar cf c/uszus METHOD AND APPARATUS FOR REDUCING POWER REQUIRED BYMOVING SUCTIUN BOX COVER Edgar J. Justus, Beloit, Wis., assignor toBeloit Iron Works, Beloit, Wis, a corporation of Wisconsin Filed Jan.14, 1958, SerflNo. 708,878

Claims. (Cl. 162-367) The instant invention relates to paper machines,and more particularly, to an improved suction box structure for papermachines.

As is well known, the conventional Fourdrinier type paper machinecomprises a looped traveling forming wire presenting a forming reachextending from a breast roll (whereat stock is flowed onto the wire) toa suction couch roll (at approximately the location at which the formedWeb is removed from the wire). Various dewatering devices are mountedbeneath this reach of forming wire and one of the more common dewateringdevices is known as the suction box, which presents a flat perforate topto the bottom side of the wire. The interior of the suction box isexhausted so as to assist in drawing Water from the web through the wireand through the perforations in the flat top of the suction box. Thepressure differential thus created tends to hold the traveling wire downagainst the stationary flat tops of the suction box so as to increasewear on the wire.

Various devices have been suggested for the purpose of avoiding thiswear on the wire caused by drawing the moving wire over the fixedsuction boxes; and one of the most well known of these devices is oftenreferred to as the Evans Roto Belt, which is described and claimed inUS. Patent No; 2,039,308 issued to William P. Evans on May 5, 1936. Inthe Evans structure a perforated moving belt with solid edges isinstalled between the traveling Fourdrinier wire and the suction boxcovers in an attempt to reduce wire wear and also suction box coverwear. A difficulty with this device has been the very large powerrequirement in order to drive the ap paratus at practical paper machinespeeds. The pressure differential in the suction box, of course, causesthe belt to be urged against the suction box covers by relatively greatforces and a substantial amount of power is required to drag thebeltover the suction box covers. The power must be supplied either throughthe wire itself or by means of an independent drive, but in either casesubstantial difficulties are encountered in operating at the highmachine speeds currently employed. In addition, great difficulty hasbeen found in guiding the belt properly across the suction box covers,also because of the frictional drag created by attempting to move thebelt across the suction box covers.

The instant invention resides in a novel, simple and particularlyeffective arrangement for overcoming these difiiculties. The instantinvention is based upon the discovery that probably the greatest sourceof difliculty is the tendency for the rubber belt to wipe land areas ofthe suction box cover dry, thus removing water which is one of thebetter fluid lubricants for rubber. These land areas between the suctionbox perforations or drainage holes coincide with land areas in the beltbetween drainage holes in the belt and the movement of the rubber beltover the suction box cover wipes the land areas in the cover dry andcreates very great frictional drag. In accordance with the teachings ofthe instant invention,

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grooves are mounted in the land areas of the suction box cover and afluid lubricant, e.g., a liquid, preferably water, is forced underslight pressure into such grooves so as to continuously lubricate theinner faces between land areas on the suction box cover and on thebottom of the belt. The force with which these land areas are urgedtogether at the inner face is such that a controlled but slight amountof water may flow from the grooves into the drainage holes in thesuction box cover, thus effecting no appreciable increase in the load ofwater that must be drawn off through the suction-boxes, while greatlyreducing the power requirement for driving the belt.

It is, therefore, an important object of the instant invention toprovide an improved paper machine, and more particularly, to provide animproved suction box structure.

It is a further object of the instant invention to provide an improvedsuction box structure for dewatering a web on a traveling wire,comprising a suction box having a generally flat top with perforationstherein and land areas intermediate the perforations, an endlessflexible perforate belt covering the suction box top and adapted tosupport and engage the bottom side of the wire, means defining shallowgrooves in the land areas of said suction box top, and means connectedto a source of liquid under pressure communicating with the grooves forflowing liquid between the bottom side of the belt and the suction boxtop to lubricate the same.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed description thereof and the drawings attached heretoand made a part hereof.

On the drawings:

Figure 1 is an essentially diagrammatic elevational view of a papermachine having a suction box structure embodying the instant invention;

Figure 2 is an enlarged view of the suction box structure shown inFigure 1;

Figure 3 is an enlarged sectional fragmentary detail view takensubstantially along the line IIIIII of Figure 2, with parts showndiagrammatically;

Figure 4 is a sectional elevational fragmentary view taken substantiallyalong the line IV-IV of Figure 3; and

Figure 5 is a fragmentary detail top plan view of a suction box coverembodying the instant invention.

As shown on the drawings:

In Figures 1 and 2 there is shown a paper machine indicated generally bythe reference numeral 10 comprising a looped forming Wire 11 trainedover a breast roll 12, table rolls 13, suction boxes 14, a couch roll15, a turning roll 16, and return rolls 17. Stock is deposited on theupper wire run 11a from a head box 18 in the region of the breast roll12 and the stock is dewatered during its travel on the upper wire run11a to form a web W which is removed from the wire 11 by a pickup felt19 urged against the web W by a suction pickup roll 20. A rotary belt 21mounted on rolls 22, 23 and 24 is interposed between the suction boXes14 and the wire run 11a.

As best shown in Figure 2, the wire run 11a travels in the directionindicated by the arrow with the Web W thereon. The traveling endlessbelt 21 engages the bottom side of the Wire and is mounted for travelingon a roll 22 closely spaced from the oncoming side of the suction boxes14, 14 and a roll 23 closely spaced from the off-running side of thesuction boxes 14, 14 (with a third guide roll 24). The rolls 22 or 23,or both, are driven. As here shown, the roll 23 is driven by suitabledrive means 25 (shown diagrammatically). The wire run 11a may also beused to drive the belt 21.

Each of the suction boxes 14, 14, 14 is equipped with a generally flattop 14a having perforations 14b therein which open into the interior14c. Exhaust means in the form of a pump 26 (shown diagrammatically)connect to drop legs 14d of each of the suction boxes 14 for purposes ofexhausting the interiors 14c, 14c, 14c to effect dewatering of the web Wthrough the perforations 14b.

As indicated in Figure 2 the perforations 14b in the suction box top 14aare spaced longitudinally in the direction of wire travel. As shown inFigure 3, the perforations 14b in the suction box top or cover 14:: arealso spaced laterally and there are land areas Me on the generally flatupper face of the cover 14a. Such land areas 144 are intermediate theperforations 14b and actually provide the supporting surface for thecover 14a that supports the traveling belt 21 moving thereover. In thepractice of the instant invention, it will be seen that the land areas14c are provided shallow grooves 14 which face the belt 21 travelingthereover. These shallow grooves 14 are closed off from the interior 14cof the suction box 14.

As here shown the land areas 142 mounting the grooves 14f and thegrooves ldfthemselves extend longitudinally of the direction of wiretravel. The machine direction is indicated in Figures 4 and 5 by arrows.The grooves 14 extend from near the off-running edge 14g (Figure 4) ofthe suction box covers 1411 to near the oncoming edge (not shown).

As indicated diagranunatically in Figure 3, means conneoted to a sourceof liquid under pressure communicate with the grooves 14f for flowingliquid between the bottom side of the belt 21 and the suction box top14a to lubricate the same. Such means indicated generally at 39 inFigure 3 are shown diagrammatically and they in clude a pump 31, apressure control valve 32 (for maintaining a predetermined pressure inthe water header 33), and conduits extending from the header 33 to thegrooves 14- which conduits are indicated generally at 34. Referring toFigure 4, it will be noted that water under pressure flows from theheader 33 through the conduit 34 into the groove 14 As indicated by thearrows in light lines in Figure 5, the water flows from the grooves 14falong the land areas 14c and ultimately to the perforations 14b in thecover 7140. This flow indicated in Figure 5 is very slight and iscontrolled by the pressure of the belt 21 against the land areas 142,but the flow is suflicient to lubricate the rubber belt 21 and toprevent the dragging of the rubber belt 21 over dry land areas 14:2.

The belt 21 is, of course, provided with perforations or drainage holes,indicated at 21a in Figures 3 and 4. The drainage holes 21a are somounted in the traveling belt 21 that they do not align themselves withthe grooves 14f in the suction box cover 14a. In this way water is notforced back up through the drainage holes 21a. Instead, the drainageholes 21a periodically align themselves with the perforations 14b in thesuction box cover 14a. The bottom side of the belt 21 has, of course, anumber of openings therein formed by the drainage holes 21a.Intermediate the drainage holes 21a there are land areas 21b on thebottom side of the belt 21. These land areas normally cover the grooves14 in the land areas 14e on the top side of the suction box cover 14a.These belt land areas 21b are urged downwardly against the suction boxland areas 14c by the pressure difierential created by the suction box14. For this reason water is urged into the grooves 14 under slightpressure to efliect continuous seepage of water between the faces of theland areas He and 21b. Water seepage at this interface 14a, 21b isnecessary to prevent the rubber belt 21 from wiping the land areas 142dry and thereby increasing the frictional drag. Preferably the seepageof water is very slight, so as not to overload the water removal systemfor the suction box 14.

The top side of the belt 21 is preferably provided with a plurality oflongitudinally spaced laterally extending grooves or channels 210. Eachsuch groove 210 is provided with one or more drainage holes 21a, and ashere shown the groove 210 (of Figure 3) is provided With a plurality ofdrainage holes 21a. The same structure is employed for each of the othergrooves 21c shown in cross-section in Figure 4.

Processwise, the instant invention involves a method of dewatering apaper web W traveling upon a wire 11a passing over a stationary suctionbox cover 14a, that comprises passing a perforate elastomer belt 21between the wire 11a and the suction box cover 1411, exhausting thesuction box 14 to urge the belt 21 and the box cover 14a toward surfaceto surface contact, and forcing fluid lubricant, e.g., a liquid betweenthe belt 21 and the cover 14a to maintain a lubricating filmtherebetween. It will be appreciated, of course, that the instant systemcom-prises an improved distribution system for the fluid lubricant, i.e.means for distributing the fluid lubricant between the land area 142(Figs. 4- and 5) and the belt 21, said means comprising passages 34, 34extending through the land area and spaced within said lands to maintainsaid lubricant between said belt 21 and said land areas (along theregions generally indicated by the dashed-line arrows on the lands 14c,of Fig. 5).

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

1. An improved suction box structure for dewatering a web on a travelingwire, comprising a suction box having a generally flat top with drainperforations therein and land areas intermediate the perforations ofsubstantially greater total area than the total area of saidperforations, an endless flexible perforate belt covering the suctionbox top and adapted to support and engage the bottom side of the wire,means for distributing a fluid lubricant between the land area and saidbelt, said means comprising passages extending through the land area andspaced within said lands to maintain said lubricant between said beltand said land areas, and means connected to a source of fluid lubricantunder pressure communicating with the passages for flowing fluid film inopposite transverse directions across the land areas and toward thedrain perforations between the bottom side of the belt and the suctionbox top to lubricate the same.

2. An improved suction box structure for dewatering a web on a travelingwire, comprising a suction box having a generally flat top with drainperforations therein opening into an interior portion of the box andland areas intermediate the perforations, the total area defined by saidperforations being substantially less than the total area of said landareas, an endless flexible perforate belt covering the suction box topand adapted to support and engage the bottom side of the wire, meansdefining a plurality of generally parallel shallow grooves in the landareas of said suction box top closed otf from said interior portion andextending continuously in a longitudinal direction from adjacent theoncoming edge to adjacent the off-running edge of said box top, meansexhausting said interior portion to effect dewatering throughperforations in the box top and the belt, and means connected to asource of liquid under pressure communicating with the grooves forflowing a liquid film in opposite transverse directions across the landareas and toward the drain perforations between the bottom side of thebelt and the suction box top to lubricate the same, the area defined bysaid grooves being essentially coextensive with the interior portion ofthe suction box.

3. In a paper machine, a traveling forming wire carrying a paper webthereon, a traveling endless belt engag ing the'bottom side of the wire,means defining laterally extending grooves with drainage holes and withclosed selvedges in said belt, a suction box having a generally flat topwith a plurality of transversely spaced rows of longitudinally alignedspaced drain perforations therein and land areas intermediate theperforations of substantially greater total area than the total area ofsaid perforations, means defining shallow grooves in the land areas ofsaid suction box top and said land areas and said grooves extendinglongitudinally in the direction of wire travel, and means connected to asource of liquid under pressure communicating with the grooves forflowing a liquid film in opposite transverse directions across the landareas and toward the drain perforations between the bottom side of thebelt and the suction box top to lubricate the same.

4. In a paper machine, a traveling forming wire carrying a paper webthereon, a traveling endless belt engaging the bottom side of the wire,means defining laterally extending grooves with drainage holes and withclosed selvedges in said belt, a suction box having a generally fiattopwith a plurality of transversely spaced rows of longitudinally alignedspaced drain perforations therein opening into an interior portion ofthe box and land areas intermediate the perforations of substantiallygreater total area than the total area of said perforations, meansdefining a plurality of generally parallel, continuous andlongitudinally extending shallow grooves in the land areas of saidsuction box top closed off from said interior portion, means exhaustingsaid interior portion to efiect dewatering through perforations in thebox top and the belt, and means connected to a source of liquid underpressure communicating with the grooves for flowing a liquid film inopposite transverse directions across the land areas and toward thedrain perforations between the bottom side of the belt and the suctionbox top to lubricate the same, the area defined by the perforations inthe suction box top being substantially coextensive with the areadefined by the grooves in said top;

5. In a paper machine, a traveling forming wire carrying a paper webthereon, a traveling endless belt having its top engaging the bottomside of the wire, means defining laterally extending grooves withdrainage holes connecting therewith and with closed selvedges in saidbelt on its top side and land areas intermediate the drainage holes onthe bottom side of the belt, a suction box having a generally fiat topwith perforations therein and land areas intermediate the perforations,the total area defined by said perforations being substantially lessthan the total area of said land areas, means defining longitudinallyextending shallow grooves in the land areas of said we tion box top,said grooves being normally covered by the land areas on the bottom sideof the belt, and means connected to a source of liquid under pressurecommunicating with the grooves for flowing liquid at a pressure inexcess of static pressure between the bottom side of the belt and thesuction box top to lubricate the same with a relatively thin liquid filmflowing in opposite transverse directions across the land areas andtoward the perforations.

